1. Pre-Chamber Ignition A road towards High Efficiency Natural Gas Engines
Ashish Shah, Per Tunestål and Bengt Johansson Lund University, Sweden
Energirelaterad fordonsforskning 2014
Gothenberg, Sweden

2. Outline Introduction Motivation and relevance
Past activities and results obtained
Future plans

3. Introduction Administrative details of the project Name
Gas Engine Project
Timeline
Phase 6: to
Phase 7: to
Principal beneficiary
Lund University
Other partners in the project
Volvo, Volvo Cars, Scania, Cummins, Toyota, Chevron, Loge, Dantec, Swedish Biomimetics and Wärtsilä
Parent program
Competence Center Combustion Processes, KCFP
Total support
KCFP in total is 101 MSEK for phase 7. The gas engine project part of that is 12.12MSEK.

4. Introduction (cont.)
Aim – Develop combustion strategies for internal combustion engines operating on gaseous fuels for heavy duty applications with comparable or better fuel efficiency and operating load range than diesel counterparts
Current focus is on study of alternative ignition techniques for heavy duty natural gas engines with the following objectives:
Extend the limit of combustion dilution with excess air, Exhaust Gas Recirculation (EGR) or both.
Increase the maximum operating load

5. Motivation and Relevance
Natural Gas – an attractive alternative fuel
Lower specific CO2 emissions
Availability – naturally occurring and renewable alternatives (e.g. biogas etc.)
Variety of applications – heavy duty on-road vehicles (e.g. trucks with LNG), marine engines and power generation (e.g. Wärtsilä and MAN products)
Increasing network on natural gas fueling stations in Sweden and worldwide.

6. Why Pre-chamber ignition?
Problems with open chamber spark ignited engines
Simple and cheap
Well developed and mature technology
Limit of dilution with excess air or EGR – combustion instability
High temperature combustion – High heat losses and NOx emissions
Maximum load limited by knock
Knock limited combustion phasing advance – loss in efficiency

7. Why Pre-chamber ignition?
Pre-chamber ignition – a possible solution
(≈ 5% Vc)
Spatially distributed ignition source
Less affected by cyclic variation of main chamber charge motion
Burning jets provide much higher ignition energy than a spark
Pre-chamber over heating may cause charge pre-ignition
Resulting ignition mechanism is less understood due to its fluid dynamic and chemical kinetic complexities
(≈ 95% Vc)

8. Different strategies

9. Experiments and Results obtained so far…

10. Experimental Setups

11. Experimental Setups (cont.)

12. Lean limit with excess air

13. Indicated Efficiency

14. NOx emissions

15. Effect of Pre-chamber geometry

16. Effect of Pre-chamber geometry (cont.)

17. Conclusions
A pre-chamber ignition device without additional fueling reduces cyclic variations of combustion event but is not capable of considerably extending the lean limit.
A pre-chamber with additional fueling can considerably extend the lean limit of operation and hence improve indicated efficiency and reduces NOx emissions
A larger pre-chamber provides higher ignition energy but size is limited by fraction of pre-chamber combustion before main chamber ignition.

18. Future Plans
Study pre-chamber ignition at full load conditions (IMEPg > 20 bar)
CFD simulations of pre-chamber jets based on experimental pressure data to understand ignition mechanism resulting from PC jets
Optical diagnostics of pre-chamber ignition in the Wärtsilä large bore engine through optical access to the main chamber and/or pre-chamber.
Optical diagnostics of knock phenomenon with pre-chamber ignition.

19. Future Plan (cont.)

20. Thank you Comments/Questions?
Ashish Shah Ph.D Student Division of Combustion Engines Lund University